Assessment of sensory function in the operating room utilizing cerebral evoked potentials: a study of fifty-six surgically anesthetized patients.

Sensory evoked potentials (visual, auditory, and somatosensory) were recorded from 56 patients at the time of surgery to monitor neural function during critical portions of the operation. Fluctuations in latency and amplitude of the components occurred with changes in depth of anesthesia, blood pressure, irrigation, and neural tissue manipulation. Most of these changes were only transient. Permanent changes in evoked potentials occurred with decompression of neural tissue and prolonged retraction. Transient changes were not associated with any change in postoperative neurological function whereas changes in evoked potentials that persisted through the operation were highly likely to be associated with a postoperative change.